// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_
#define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_

#include <vector>

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/singleton.h"
#include "content/common/accessibility_mode_enums.h"
#include "content/public/browser/browser_accessibility_state.h"

namespace content {

// The BrowserAccessibilityState class is used to determine if Chrome should be
// customized for users with assistive technology, such as screen readers. We
// modify the behavior of certain user interfaces to provide a better experience
// for screen reader users. The way we detect a screen reader program is
// different for each platform.
//
// Screen Reader Detection
// (1) On windows many screen reader detection mechinisms will give false
// positives like relying on the SPI_GETSCREENREADER system parameter. In Chrome
// we attempt to dynamically detect a MSAA client screen reader by calling
// NotifiyWinEvent in NativeWidgetWin with a custom ID and wait to see if the ID
// is requested by a subsequent call to WM_GETOBJECT.
// (2) On mac we detect dynamically if VoiceOver is running.  We rely upon the
// undocumented accessibility attribute @"AXEnhancedUserInterface" which is set
// when VoiceOver is launched and unset when VoiceOver is closed.  This is an
// improvement over reading defaults preference values (which has no callback
// mechanism).
class CONTENT_EXPORT BrowserAccessibilityStateImpl
    : public base::RefCountedThreadSafe<BrowserAccessibilityStateImpl>,
      public BrowserAccessibilityState {
public:
    BrowserAccessibilityStateImpl();

    static BrowserAccessibilityStateImpl* GetInstance();

    void EnableAccessibility() override;
    void DisableAccessibility() override;
    void ResetAccessibilityMode() override;
    void OnScreenReaderDetected() override;
    bool IsAccessibleBrowser() override;
    void AddHistogramCallback(base::Closure callback) override;

    void UpdateHistogramsForTesting() override;

    AccessibilityMode accessibility_mode() const { return accessibility_mode_; };

    // Adds the given accessibility mode flags to the current accessibility
    // mode bitmap.
    void AddAccessibilityModeFlags(AccessibilityMode mode);

    // Remove the given accessibility mode flags from the current accessibility
    // mode bitmap.
    void RemoveAccessibilityModeFlags(AccessibilityMode mode);

    // Accessibility objects can have the "hot tracked" state set when
    // the mouse is hovering over them, but this makes tests flaky because
    // the test behaves differently when the mouse happens to be over an
    // element.  This is a global switch to not use the "hot tracked" state
    // in a test.
    void set_disable_hot_tracking_for_testing(bool disable_hot_tracking)
    {
        disable_hot_tracking_ = disable_hot_tracking;
    }
    bool disable_hot_tracking_for_testing() const
    {
        return disable_hot_tracking_;
    }

private:
    friend class base::RefCountedThreadSafe<BrowserAccessibilityStateImpl>;
    friend struct base::DefaultSingletonTraits<BrowserAccessibilityStateImpl>;

    // Resets accessibility_mode_ to the default value.
    void ResetAccessibilityModeValue();

    // Called a short while after startup to allow time for the accessibility
    // state to be determined. Updates histograms with the current state.
    void UpdateHistograms();

    // Leaky singleton, destructor generally won't be called.
    ~BrowserAccessibilityStateImpl() override;

    void UpdatePlatformSpecificHistograms();

    AccessibilityMode accessibility_mode_;

    std::vector<base::Closure> histogram_callbacks_;

    bool disable_hot_tracking_;

    DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityStateImpl);
};

} // namespace content

#endif // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_
